The US has accused Chinese hackers it described as “state-backed” of breaking into NASA, the Federal Reserve, and other sensitive government networks, just weeks before Chinese President Xi Jinping is expected in Washington for talks with President Donald Trump.

Beijing rejected the allegations. The Chinese Embassy in Washington said China “opposes and combats all forms of cyberattacks” and urged the US to “stop using cybersecurity issues to smear or discredit China.”

The Justice Department and FBI announced on Wednesday that they seized three internet domains linked to two hacking platforms allegedly operated by a Chinese group known as QTFY. The US authorities claimed the operation targeted NASA, the Federal Reserve, the Senate, and several government departments, as well as hospitals, telecommunications providers, power companies, financial institutions, and defense contractors.

Washington described the campaign as Chinese state-sponsored activity and alleged that the company behind it provided hacking services to China’s Ministry of State Security and the People’s Liberation Army. However, officials did not disclose what sensitive information was allegedly stolen or what damage, if any, was caused.

The latest accusations come little more than a month after Trump accused Beijing of meddling in US elections, claiming China illicitly acquired 220 million American voter files during the 2020 election cycle in what he called the “largest compromise” of election data in US history.

China dismissed that allegation as “groundless” and “entirely fabricated.” Trump’s assertions of election hacking were met with skepticism even among some of his supporters, as the documents released by the White House only showed Chinese interest in collecting publicly available or commercially obtainable American voter information.

Trump openly acknowledged after meeting Xi in Beijing in May that Washington conducts extensive espionage against China.

“We spy like hell on them too,” Trump told reporters. “We do a lot of stuff to you that you don’t know about,” Trump said he told Xi, describing the two countries’ espionage activities as a “double-edged sword.”

Beijing has made similar accusations against Washington, claiming last October that the NSA conducted a years-long cyberattack on China’s National Time Service Center, which supports critical sectors including finance, energy, transportation, and defense. The NSA did not confirm or deny the allegation.

The renewed cyber accusations come ahead of Xi’s expected visit to the US on September 24. Trump said he plans to host the Chinese leader following their talks in May in Beijing, as the two sides seek to manage disputes over trade, technology, and cybersecurity, as well as the sanctions threats against nations that continue trading with Iran.